Electric switch



1918 4 Sheets-Sheet 1 G. A. BURNHAM ELECTRIC SWITCH Filed June 17.

March 18 1924.

March 1s, 1924. 1,487,087

` G. A. BURNHAM' ELECTRIC SWITCH Filed June 17, 1918 4 Sheets-Sheet 2feg,

4 Shea -Sheet 5 G. A. BURNHAM ELEcTmc swung' Filed June 17. 191e Much1s, 1924.

Patented Mar. 18, 1924.

UNITED STATES PATENT OFFICE.

GEORGE A. BURNHAM, 0F SAUGUS, MASSACHUSETTS, ASSIGNOR TO SEARS B.CONDIT, JR., 0F BROOKLINE, MASSACHUSETTS.

ELECTRIC SWITCH.

Application led .Tune 17, 1918.

operating rod and which are adapted to be moved simultaneously intocontact with the two poles of the switch to conjointly conduct currenttherebetween.

The current carried by a brush member making contact with a pole of aswitch depends to some extent upon the pressure with which the brush isforced against the pole. W'ith a plurality of independent brush mem bersall making contact with a pole of a switch, it is necessary that theyall be pressed against the pole with equal pressure in order that theymay, so far as possible, carry equal currents.

This result is usually obtained by placing shims beneath the independentbrush members and independently adjusting each brush member by theinsertion or removal of shims until the proper contact pressure isobtained.

lith continued operation of the switch, it becomes necessary to more orless frequently adjust the brush members on the operating rod tomaintain substantially equal contact pressure at all times and thusmaintain a uniform current distribution between the independent brushmembers.

The brush membersl are necessarily continually submerged in the oil ofthe switch and are accessible only by the removal of the oil receptacle.The proper adjustment ofthe brushes is difficult tor obtain, requires aconsiderable time and moreover is a very disagreeable operation sincethe contacts andA Serial N'o. 240,317.

culties which are inherent with brush mem bers which must be adjusted bythe use of shims and the like.

The means whereby I accomplish this object of my invention is in theprovision, in a switch having a plurality Vofbrush members acting toconjointly conduct current between two opposite poles of the switch, ofan independent operating-rod for every brush member, eachof the movableswitch members formed of the separate operating rods and connected brushmembers being independently adj ustably connected to the switchoperating mechanism disposed above the switch.`

Inasmuch as each brush member and operating rod is independentlya'djustably connected to the switchmechai'iism it follows that eachbrush member may be adjusted independently of any other brush member andas the connection with the operating mechanism is above the switch, itis not necessary to remove the oil receptacle to adjust the brushmembers.

Furthermore it may be seen that the multiplicity of parts which must bemanufactured and kept in stock for a line of Loil switches of varyingcapacities may be materially reduced. If the manufacturer makes aswitch, for instance, having a current carrying capacity of 1,000amperes and using one brush member and operating rod, then to constructa switch of say 2,000 amperes, it is merely necessary to take two 1,000ampere movable switch members, each comprising a brushmember andoperating rod, and arrange them to operate in parallel with a commonpole of the 2,000 ampere switch. In the saine manner, if a 4,000 ampereswitch is desired, it is simply necessary to take four 1,000 amperemovable switch members and independently connect them to the switchoperating mechanism to operate in parallel with a common pole of theswitch.

In this manner a switch of any desired large capacity may be easily andcheaply constructed from the movable switch members of switches of asmaller capacity.

In conjunction with two brush members connected to a single operatingrod, it is common to employ a single Contact block to be engaged by thedouble brush members.

The contact blocks are made exceedingly massive in construction toprovide sufficient radiating surface to perInit the conduction of thecurrent without an excessive teniperature rise.

It is well known that the current carrying capacity of a given conductorfor a given teniperature rise is dependent upon its etlective radiatingsurface.

If a conductor of a certain cross-sectional area operates successfullyto carry a certain value of current and it is desired to provide aconductor to arry say double the current7 it will not suiiice to nicrelydouble the crosssectional area ot the conductor while pref serving thesaine general shape or torni oi' the conductor, ior the doubling or thearea of copper does not, by tar, double the heat radiating area of theconductor and it becoines necessary to additionally increase the area ofthe conductor until sulicient nietal has been added to double theei'ectiye radiat ing surface.

In electric switches it has been connnon to increase the size or' thecontact blocks by adding` copper while still preserving the general orinand design ot the bloc-lis, until the block has sullicient effectiveradiatingr area to successfully carry the current. This results in ablock that is exceedinglyrv inassive in construction and exceedinglyexpensive and highly inellicient because of eddy current losses in theniass.

it, however7 instead ot increasing the niass of copper in a singlecontact block to carry the increased current, the number of the conactblocks are increased in proportion to the increase in current7 then theincrease in inass of copper bears ay niore equable ratio to the increasein current.

Consequently, a i'nrther object of iny invention is the provision ot aswitch having a plurality oi? independent contact blocks per pole withwhich the brush nienibers are adapted to inaliel contact.

I may prefer to einploy a single contact block tor two or nioreindependent movable switch ineinbers. but with a given nuinber ofmovable switch nieinbers :nie/rating` in parallel with a` connnon poleof the switch. prefer to use a plurality ot contact blocks.y r-:liichare arranged to be connected in garai lel, to torni a. connnon switchpole or stationary switch ineznber.

Ji `yet further object oi niy invention is in the provision ol aplurality ot indeiliendcnt switch studs per pole oi the switch.

l irefe to so arrange said studs that i are e ectrically independent.i'ithin the sw but may he electrically connected abore the switchwhereby lthe current distribution therein tends to becoine equalized.

Fig. i is an assembly ot three switch units embodying' iny invention andadapted lor the control of a three phase circuit.

Fig. 2 is :t sectional longitudinal elevation oi a switch unit of Fig.l.

Fig. 8 is a transverse sectional elevation of a switch alon lines. ofFigure Fig. l is a sectional detail of the operating mechanism.

Fig. 5 is a plan detail of the operating TU nieclranisin.

As here shown7 three switches cii'ibodying niy invention and adapted forthe control ol' a three phase circuit are ipported by the pipe i'raniestructure T and are secured to 7n and depe d treni a casing in which heswitch opeiatinL` nn anisni is inclosed.

aid casing` is s a ally U shaped in section and comprises the twoVertical spaced apart side walls S) and 9' and the connecting 50 bottoniwall itl. fr coi"A li arranged between the tops ot walls serres tocompletely` inclose Vthe operating` nieehanisrn arranged ther 1in andnreent the entrance of *ate/r er other i'c substance. 95

rllhe ends oi `V`aid s le wie `ic proiii l with i'ianges i2 and i neansol which the casing niay be secured to the pipe traine structure.

Each switch urit inciiides a ccfer plate lil 9G secured by inermi. cibolts i-l to t? e bottoni wall 10 et said casing; and on which the coinAponent parts ot the sn ed. )rn oil receptacle l5 is secured to saidcover plate by ineans ot iig-bolts i6 which per- 95 init the readyreinoval of the receikitacle when desired.

The "witch closed in the casing' 8 and inclndes the bars or rot and liwhich ermi iid tfzisJing;` above the l which. the niorable switclconnected.

.Sai iT and li are spaced apart a suit-able distance by ineans ol'spacinfr liioi'ls 105 and are bolted or otherwise #ecured together ie'fl'eit a. single :switch operating tend the lengt-h of units` andineniber.

f* E 7" baie operatie x @signed to the. vertical .side in lfhe distancel iii wars is ariane' pl ne. ranged at each switc if? i the ball-bearingJiritc wits! s Q0 and 20 in moving the bars 17 and 17 in a straightline. Said toggle members include the links 22 which arc pivoted to saidbars by pins 23 extended through said bars and which are also connectedby pins 24, to links 25 forming the other part of the toggles, whichlatter links are pivotally arranged on pins 2G. Said pins are arrangedbetween lugs 27 downwardly extended from the bottom wall 10 of themechanism casing into the top part ot the switch 'receptacle in order topermit a length of link sutlicient to give an adequate movement of themovable switch members. Said toggles are connected together forsimultaneous operation by the rods 28 and 28a which extend between thetoggles and are connected thereto by the pins 24.

A link 29 is connected to said rods 28 and 28 at an end toggle and at 30to a leve-r 31, pivotally arranged on a pin or shaft 32 extended betweenthe side walls 9 and 9T ot the mechanism casing. Said lever 31 is formedwith an extended lug or ear 33 which is adapted for pivotal connectionywith a rod 34 extending to the switch ope-rating handle, not shown,which may be placed in any suitable position.

It is seen that if said lever 31 is moved to the right from the positionshown in Fig. 1, the toggles will be moved from their straightenedposition and the operating members will be moved vertically downward,being guided in such movement by the ways 20, and the movable switchmembers connected to said operating members will be moved from contactwith the stationary switch members.

A movement of said lever 31 in the opposite direction serves tostraighten the toggles and to move said operating members upward and itis guided in such upward movement in substantiall a straight line by theengagement of the bal bearings 18 with the ways 20, and the movableswitch members are consequently moved into contact with the stationaryswitch members in substantially a straight line.

Shock absorbing means are provided to absorb the energy of the switchoperating member and connected mechanism in movement to open position,Said means includes plates 35 having grooves therein by'means ot whichthe plates are slidably arranged between the vertical guide members 2Oand 20a. Rods 3G are secured to the under side of said plates and areslidably arranged in the bottom wall 10 of the mechanism casing. Springs37 interposed between said bottom wall 10 and said plates 35, serve tonormally maintain said plates in position and screws1 38 secured to thelower end of said rods 36 serve to prevent said rods from being forcedfrom the bottom wall 10 by said springs.

During the latter part of the movement of the operating mechanism in amovement of' the switch into open position the bars 17 and 17a of theoperating mechanism fall into contact with the plates 35 of the shockabsorbing mechanism and the momentum ot the moving mechanism is absorbedinto coinpressing the springs 37 and thereby preventing severe stressesthat would be otherwise set up in the component parts ot' the mechanism.

The stationary switch studs are formed of a plurality ci spaced apartbars 40 which are extended through openings in bushings 41 secured inthe cover plate 13, into the interior oi the switch housing andterminate in contact blocks 42 which are slotted to rcceivetheindividual bars 40. The Contact blocks are provided with flat, broad,main contact surfaces 43 to which are secured auxiliary contact members44.

As here shown, the switch is provided with two separate switch studs Aand B each formed of a plurality of said bars 40 which are electricallyand mechanically independent within the switch housing and are extendedthrough separate insulating bushings 41 as shown and both of whichconjointly form one pole of the switch.

Above the switch housing, the switch studs A and B are secured to thebushings by means of the clamps 46 and 46@L between which the barscomprising each stud are secured. Said clamps 46a extend between bothstuds A and B and serve to electrically connect said studs and thereforetend to equalize the current flow in said studs.

A plurality of independent brush members 50 of more or less common formand construction are arranged to make independent contact between thestationary switch members and as here shown, four independent brushmembers are employed which serve collectively to carry the current fromone pole of the switch to the opposite pole.

Auxiliary Contact members 51 are arranged at the ends of a spring 52secured to each brush member 50 and are adapted to make initial contactwith the auxiliary contact plates 44 arranged on the contact blocks 42and 42a as is common practice.

Each of said independent brush members 50 is provided with anindependent operating rod 53 of an insulating material to thereby formindependent movable switch members.

Each brush member is secured to a plate p U 1. 1 11. .1.. i. Wi... .Y..1. .11, Y

D. Q C mc l Y1.. .1.. .U .1.. .1. .IL wc 1 WV.. V.. O L .1. D 1..... Y..Y1 QL .Tu Y1. ...1. Y. Y U12... H C O .u w.. 1. .Y D 1. l Y1. 1.1. 1...L

.u 1 .Y.... n.. O mv. l C .L d G n h n.110.. c @T 1. 1 1 1 ...11. 11. L0 7.1. l.. .Y... .L ...L A C 7.... .Y. .Y nu ....u 5 f Y l X1. l. :YL Lxsd 6 ary switch member comprising aA plurality connecting said studsabove said cover 10 of independent and spaced apart studs, eacli plate.

stud formed of a plurality of spaced-apart, In testimony whereof, I havesigned my electrically connected conducting bars. name to tliisspecication, in the presence of.

7. An electric switch including a cover two subscribing Witnesses.

plate and a stationary switch member com- GEORGE A. EURNHAM.

prising a plurality of independent and Witnesses:

separated studs electrically independent be- T. T. GREENWOOD,

loW said cover plate7 and means electrically Y H. B. DAVIS.

